Marine anchor chain round steel
Marine anchor chain round steel is a specialized steel used in the manufacture of marine anchor chains. It is a core material for a ship’s mooring system, and its quality is directly related to the ship’s navigational safety. As a crucial component connecting the hull to the anchor, the anchor chain must withstand the tremendous tensile and impact forces generated by the ship in wind and waves. Therefore, marine anchor chain round steel must possess high strength, high toughness, seawater corrosion resistance, and excellent weldability. This type of round steel is typically manufactured from high-quality carbon structural steel or alloy structural steel, such as 20Mn2, 25MnV, and 35CrMo. Through rigorous smelting, rolling, and heat treatment processes, its mechanical properties and quality stability meet the specifications of the International Maritime Organization (IMO) and national classification societies.
The manufacturing process for marine anchor chain round steel adheres to stringent quality control standards. First, steelmaking requires smelting in a converter or electric arc furnace, combined with off-furnace refining techniques (such as LF and VD furnaces). The levels of harmful elements such as sulfur and phosphorus in the steel are strictly controlled, with sulfur levels below 0.025% and phosphorus below 0.035%. Gas and non-metallic inclusions are also minimized to enhance the steel’s purity and toughness. Subsequently, the billet is heated to the appropriate temperature in a heating furnace before hot rolling. During the rolling process, the rolling temperature, reduction, and speed must be carefully controlled to achieve a uniform grain structure and avoid defects such as cracks and folds. After rolling, the round steel undergoes spheroidizing annealing or normalizing to eliminate internal stresses and improve machinability and weldability. High-strength anchor chain round steel also requires tempering (quenching and tempering) to achieve excellent overall mechanical properties.
In terms of performance requirements, round steel for marine anchor chains must meet strict mechanical performance indicators and quality inspection standards. Depending on the strength grade, its tensile strength is usually between 600-900MPa, the yield strength is not less than 360MPa, and the elongation must be greater than 14% to ensure that the anchor chain does not suffer brittle fracture when subjected to tension. Impact toughness is one of the key indicators, requiring the impact energy (AKV) to be no less than 40J at a low temperature of -40°C to ensure that the round steel can still maintain good toughness in cold waters. In addition, the surface quality of the round steel must be strictly controlled, and there must be no defects such as cracks, scars, and folds. The diameter tolerance must be controlled within ±0.5 mm to ensure the quality stability of subsequent anchor chain welding. Each batch of round steel is subject to multiple tests such as chemical composition analysis, mechanical property testing, and non-destructive testing, and can only be shipped after passing the test.
In application scenarios, the specifications and performance of marine anchor chain round steel must be selected based on the vessel type, tonnage, and navigation area. For small vessels (such as coastal cargo ships and fishing boats), 20Mn2 anchor chain round steel with a diameter of 20-40 mm is typically used to meet general anchoring needs. For large ocean-going vessels (such as container ships and oil tankers), high-strength anchor chain round steel with a diameter of 50-100 mm, such as 25MnV and 35CrMo, is required to withstand greater tension and impact forces. Special vessels such as polar research vessels and icebreakers require anchor chain round steel with excellent low-temperature toughness to ensure safety in extreme environments. After being forged, welded, and heat-treated, anchor chain round steel is made into anchor chain, it is used for anchoring and mooring operations, providing a critical guarantee for docking, positioning, and weathering ships.
Industry trends indicate that the production of round steel for marine anchor chains is moving towards higher strength, improved low-temperature toughness, and superior corrosion resistance. With the growth of larger ships and the development of ocean-going shipping, the strength requirements for anchor chain round steel are constantly increasing. Research and development of ultra-high-strength anchor chain round steel with a grade of 690MPa or higher has become a hot topic, as it can reduce the diameter and weight of the anchor chain, thereby reducing the ship’s load. At the same time, to meet the needs of polar shipping, research has made progress in improving the low-temperature toughness of low-alloy, high-strength anchor chain round steel. By adding alloying elements such as nickel and vanadium, the round steel can maintain good impact toughness at -60°C. Furthermore, the application of surface treatment technologies (such as sherardizing and anti-corrosion coatings) can improve the seawater corrosion resistance of anchor chain round steel and extend its service life. In the future, with the promotion of the green ship concept, the production of round steel for marine anchor chains will place greater emphasis on environmental protection and resource conservation, promoting the sustainable development of the industry.
